Emissions derived from maritime transport and inland shipping include carbon dioxide (CO2), nitrogen oxides (NOx), and sulphur oxides (SOx). Environmental studies have shown that marine diesel engines are the largest atmospheric polluters of the two latter: NOx and SOx.
Recent international regulations and commitments seek to limit exhaust gas emissions, however, there is little experience in shipping related emission-reducing technologies, relative to the industrial and energy sector. Moreover, in the shipping industry, the removal of NOx, SOx and CO2 from exhaust gases is commonly done separately. Combining these methods, such as combining SO2 scrubbing together with selective catalytic reduction (SCR) followed by CO2 capture, is extremely costly. Therefore, the effective, efficient and simultaneous removal of pollutants from engine exhaust gas is an important part of marine commerce.